Can My Static IP Change

I just got a new comcast gateway..... now it seems my static IP has changed! It does not appear to be what it used to be and now appears to be what my former "Gateway IP" was......

I am confused!

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Accepted Solution

train_wreck

Gold Problem solver

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610 Messages

9 years ago

You say "each PC has a network card set to get a static IP from the gateway" This does not make sense. The Windows machine should be configured either statically with the Comcast-provided IP information, or automatically. If I had to guess, I would say that right now, both PCs are actually set to automatic (DHCP). I know with my Cisco DPC3939B, by default if I plug a computer into it, the computer will receive an IP address from within 10.1.10.2-10.1.10.254, and it will appear on the internet as coming from my "Default Gateway" IP.

I will state my usual recommendation; if you have a static IP, then purchase a standalone router, configure the router with a static WAN address of your Comcast-provided IP, plug the WAN interface into the Comcast gateway, and plug all of your devices into the router's LAN.

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Accepted Solution

Heather_A

New problem solver

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24 Messages

9 years ago

What I am saying is that originally my static IP from comcast was 96.89.208 and I was told that the comcast gateway IP was 96.89.208.14

Now it seems they are saying my static IP is what they had said the gateway IP was.

I do not even see anywhere to change any of this! The place were it seems I might now appears to have very odd settings for IP entries... what look more like IPv6 addresses!

I also try to go to online sites to check what my IP is. Some show it as 96.89.208.14 and some show this long number that looks almost like a MAC address.

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Accepted Solution

train_wreck

Gold Problem solver

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610 Messages

9 years ago

My apologies; I misunderstood your meaning of the phrase "static IP". Yes, in your configuration, what you are seeing is normal for the newer Comcast gateways. (I'm guessing you have either a Netgear CG3000DCR or a Cisco DPC3939B). The gateway will provide an internal LAN subnet of, by default, 10.1.10.0. The internal DHCP server will hand out addresses from within this subnet to clients who request them. The gateway will then perform NAT on the outgoing internet-bound traffic from this internal LAN, and the address it will NAT to is the public "Default Gateway" IP. All of this functionality is in addition to the gateway's Comcast-provided public static IPs; the gateway can allow access to/from both internal 10. LAN clients and public static IP configured devices, simultaneously.

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train_wreck

Gold Problem solver

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610 Messages

9 years ago

Can you describe what equipment is connected to the gateway, and how each device is configured?

Typically, you will either assign a computer/device with your Comcast-provided static IP configuration (IP, subnet mask, default gateway, DNS), or more commonly use a separate router with its WAN interface configured with the Comcast static IP.

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Heather_A

New problem solver

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24 Messages

9 years ago

My issue is the actually static IP. When I got the service I was told it was 96.89.208.13 and that my "gateway IP" was 96.89.208.14 ............. Now it seems my static IP is the 96.89.208.14

Also when I go to a site were you can check your IP, it seems to give me what looks like a MAC Address.... the online site says my public IP address is 2601:18c:c502:1d00:3ccf:9875:c114:a485

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Heather_A

New problem solver

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24 Messages

9 years ago

I have the comcast gateway. I have two PC connected to the gateway. Each PC has a network card set to get a static IP from the gateway.

Those all seem fine. The question is just why my static IP seems to have gone from 99.89.208.13 to 96.89.208.14

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VBSSP-RICH

Advocate

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1.4K Messages

9 years ago

Hello Heather_Adams,

I would first recommend you View your Static IP information and determine if the static IP subnet mask 255.255.255.XXX is a 1 (XXX=252), 5 (XXX=248) , or 13 (XXX=240) block. From your latest post, it appears that you Static IP Gateway address (programmed within the WAN of your Comcast Gateway is 96.89.208.14 if you have a 1 block static IP. Whenever you program any device's network configuration to have a static IP, you must always enter in the routable static IP address, the static IP Gateway address, and the static IP Subnet mask. It is also good networking practice to also enter in the Domain Naming Server Primary (75.75.75.75) or Secondary (75.75.76.76) addresses.

Let us know what size static IP you have.

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Heather_A

New problem solver

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24 Messages

9 years ago

I set up each computers network card to get a specific IP on the network. This is unrelated to the static IP from comcast.

This just makes it so each computer on the network always receives the same IP from the router. This has nothing to do with the static IP from comcast.

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